You Cannot Access an EFI System Partition with the Mountvol Utility in a WinPE Environment


If you use the Mountvol utility (Mountvol.exe) in a Windows Preinstall Environment (WinPE) on either a Windows XP-based or Windows Server 2003-based computer, you cannot gain access to the Extensible Firmware Interface (EFI) system partition by using the mountvol /s command. For example, if you try to use the mountvol x: /s command, you may receive the following error message:
The system cannot find the file specified.


This behavior occurs because the Mountvol utility is not supported in WinPE environments.


To work around this behavior, use the Diskpart utility (Dispart.exe) instead of the Mountvol tool. To use the Diskpart utility:
  1. Click Start, click Run, type diskpart in the Open box, and then click OK.
  2. When the Diskpart utility starts, type select disk n at the prompt (where
    n is number for the mapped ESP disk), and then press ENTER.
  3. Type select partition
    at the prompt (where
    n is number for the mapped ESP partition), and then press ENTER.
  4. Type assign letter=x at the prompt (where
    x is the drive letter that you want to assign), and then press ENTER.
After you follow these steps, you can access an EFI system partition by using the drive letter that you assign to the partition with the Diskpart utility.


This behavior is by design.


For additional information about how to use the Mountvol utility to access an EFI system partition on computers that are running either Windows XP or Windows Server 2003, click the following article number to view the article in the Microsoft Knowledge Base:
294773 HOW TO: Access an EFI Partition in Windows XP 64-Bit Edition